A person skilled in the art of rolling bearing technology is generally familiar with the fact that single-row deep groove ball bearings are rigid, non-dismantlable radial rolling bearings which are characterized primarily in that their radial and axial load capacity is equally high, and in that, on account of their low friction, they have the highest speed limits of all bearing types. Said deep groove ball bearings have been known for a long time and are composed substantially of an outer bearing ring and an inner bearing ring and of a number of balls, which are arranged between the bearing rings, as rolling bodies, which are guided at uniform intervals with respect to one another by means of a bearing cage in in each case groove-shaped ball raceways in the inner side of the outer bearing ring and in the outer side of the inner bearing ring. The balls are introduced into radial ball bearings of said type by means of the eccentric assembly process known from DE 168 499, in which the two bearing rings are arranged eccentrically with respect to one another and the free space between the bearing rings which is generated in this way is filled with balls, which are subsequently distributed with a uniform spacing to one another on the pitch circle of the ball raceways.
In practice, however, it has been found that deep groove ball bearings of said type are nevertheless limited in terms of the load capacity of the bearing on account of the small maximum number of balls which can be installed, which is dependent on the dimensions of the inner and of the outer bearing ring and on the ball diameter. In the past, several solutions have therefore been proposed, the aim of which has been to obtain an increase in the load capacity of deep-groove ball bearings by increasing the number of balls.
One such option for increasing the number of rolling bodies in a radial rolling bearing is known for example from DE 43 34 195 A1. In said radial rolling bearing, which is embodied as a single-row deep groove ball bearing, the rolling bodies are however formed not by balls but by so-called spherical disks which are formed with two side surfaces, which are flattened symmetrically from a spherical basic shape and which are arranged parallel to one another. Here, the width of said spherical disks between their side surfaces is smaller than the spacing between the inner side of the outer bearing ring and the outer side of the inner bearing ring, such that when filling the bearing, the spherical disks can be inserted into the bearing through the spacing between the inner ring and outer ring and can then be rotated through 90° into the raceways of the bearing rings. Since it is possible with this assembly method to obtain smaller spacings between the individual rolling bodies, it is therefore possible for a higher overall number of rolling bodies to be inserted into the radial rolling bearing. However, in order to prevent contact between the rolling bodies and self-rotation of the rolling bodies transversely with respect to the running direction during operation of the bearing, said rolling bearings are also held at uniform intervals with respect to one another and guided axially in a bearing cage. Here, one of the proposed cage designs is a bearing cage which is composed of two ring halves and in which depressions are formed into each of the ring halves corresponding in each case to the number of spherical disks, which depressions engage into complementary central depressions in the side surfaces of the spherical disks. Here, the depressions in the side surfaces of the spherical disks are connected to one another by means of a central passage bore through which the two ring halves are connected to one another by means of rivets, such that the spherical disks are firmly fixed with respect to one another in the circumferential direction. Between the depressions, the two ring halves of the bearing cage each have sections which run straight along the side surfaces of the spherical disks and which, in interaction with the rivets which serve as rolling axles of the spherical disks, serve to prevent self-rotation of the rolling bodies transversely with respect to their running direction.
It has however proven to be disadvantageous that a bearing cage of said design does not make allowance for the entire kinematic behavior of the rolling bodies, which are embodied as spherical disks, which occurs under different bearing loadings, and therefore said bearing cage would appear to be unsuitable for special rolling bodies of said type. For example, it was determined that spherical disks as rolling bodies in radial rolling bearings run in a stable fashion in their rolling body raceways without tilting movements on account of the occurring centrifugal effect, and require no axial guidance by the bearing cage. However, if the bearing speed falls below a permitted minimum speed, a so-called tumbling effect occurs, in which the spherical disks tend to roll in their raceways in a sinusoidal fashion transversely with respect to the running direction. Here, contact occurs between the raceway edges of the spherical disks and the straight sections of the two ring halves of the bearing cage, as a result of which friction heat is generated to such an extent that the operating temperature in the radial rolling bearing rises. Here, the friction between the spherical disks and the bearing cage can become so intense that the permissible operating temperature of the bearing is exceeded and the required lubricating film between the spherical disks, the bearing cage and the bearing rings becomes locally separated or the lubricant is partially burned, such that the bearing cage is destroyed and the bearing fails prematurely. It was likewise found that, with a bearing cage of said type, a similar effect which likewise leads to its destruction occurs in that it is not possible for the spherical disks, on account of their mounting between the two ring halves on the rivets of the bearing cage, to be aligned to the respective pressure angle of the radial rolling bearing under mixed radial and axial loading of the radial rolling bearing. As the spherical disks seek to self-align to the pressure angle of the radial rolling bearing under such loadings of the radial rolling bearing, contact likewise occurs between the side surfaces of the spherical disks and the straight sections of the ring halves of the bearing cage, and contact occurs between the central passage bore in the spherical disks and the rivets of the bearing cage, such that excess friction heat was generated in the radial rolling bearing under such conditions too. Finally, a bearing cage of said type for spherical disks has also proven to be disadvantageous with regard to the production costs of radial rolling bearings fitted with such bearing cages, since the production of said bearing cage, and in particular the assembly of said bearing cage which must take place into the fitted bearing by means of rivets, is relatively complex.